The present invention relates to a cylindrical type alkaline storage battery.
There are a variety of cylindrical type storage batteries available at present, and typical ones are a nickel-cadmium storage battery, a nickel-hydrogen storage battery and the like. These batteries are suitable as a power source for small size equipment and are widely used in various kinds of applications such as a portable telephone, a notebook PC and the like. As the equipment using a battery becomes smaller in size, it is required that a cylindrical type alkaline storage battery should be the safer in operation, smaller in size and larger in capacity.
FIG. 5 is a schematic cross-sectional view of a prior art cylindrical type alkaline storage battery D. In FIG. 5, the reference symbol D1 is a sealing plate, reference symbol 1 is a conductive filter, reference symbol la is a gas venting hole located in the center of the filter 1, reference symbol 2 is a safety valve, reference symbol 4 is an insulating gasket, reference symbol 5 is a metallic case, reference symbol 6 is a belt-shaped positive electrode plate, reference symbol 7 is a belt-shaped negative electrode plate, reference symbol 8 is a separator, reference symbol 9 is a lead tab electrically connecting the positive electrode plate 6 to the filter 1, reference symbol 10 is a lead tab electrically connecting the negative electrode plate 7 to the inner surface of the case 5, reference symbol 11 is an insulating ring, reference symbol 14 is a cap-shaped terminal plate of the prior art sealing plate D1, reference symbol 14a is a top part of the prior art cap-shaped terminal plate 14 and reference symbol 14b is a Range of the prior art cap-shaped terminal plate 14.
As shown in FIG. 5, the belt-shaped positive electrode plate 6 and negative electrode plate 7 are wound in a spiral with the separator 8 sandwiched there-between to form a group of electrode plates. The cylindrical type alkaline battery comprises the foregoing group of electrode plates, the metallic case 5 containing the group of electrode plates and the sealing plate D1 disposed on the top part of the metallic case 5.
The safety valve 2 is disposed between the cap-shaped terminal plate 14 and the filter 1 so as to close the gas venting hole la and the foregoing filter 1 is bent in such a way as sandwiching the rim of the flange 14b and swaged thereto, thereby constituting a single-piece structure of the sealing plate D1.
The insulating gasket 4 is disposed between the part of the single-piece structured sealing plate D1, where the foregoing swaging has taken place, and the metallic case 5, and the edge of the metallic case 5 is bent forcefully inward, thereby sealing the metallic case 5 hermetically. A current path between the cap-shaped terminal plate 14 and the filter 1 is secured at the place where the swaging of the filter 1 onto the rim of the sealing plate 14 has taken place. Almost all of an electrolyte, which is not shown in FIG. 5, is held within the group of electrode plates.
In the Published Unexamined Japanese Patent Application No. H10-261397, a sealing plate of one-piece design realized by a flange of a cap-shaped terminal plate welded on a filter is disclosed, thereby demonstrating a structure, in which only the filter of the single-piece structured sealing plate is sealed via a gasket disposed between the filter and a metallic case by bending forcefully the edge of the metallic case inward.
In general, a sealing plate of a cylindrical type alkaline storage battery is required to perform such fundamental functions as hermetic sealing of the battery, safe controlling of a battery""s internal pressure and forming of a current path for battery""s charging/discharging. The amount of active material that creates battery""s capacity is limited by the internal volume of a battery case to accommodate the active material and, on the other hand, the sealing plate is a factor responsible for the reduction of the battery""s internal volume. In order for the battery""s capacity to be increased, therefore, a sealing plate structure which is as simple as possible and causes the smallest reduction to the battery""s internal volume is sought, yet, without sacrificing the aforementioned fundamental functions that the battery""s sealing plate is expected to fulfill with a high degree of reliability. From this point of view, the prior art sealing plate as described in the above has demonstrated the following problems:
First, the structural design employed in realizing a single-piece sealing plate by sandwiching the rim of the flange 14b of the cap-shaped terminal plate 14 between the bent portions of the filter 1 and swaging the metal pieces involved one another not only makes the design of needed component parts complicated but also results in a bulky structure at the swaged segment of the filter 1 due to folding over the edge thereof thereby reducing the battery""s internal volume to an intolerable extent and hindering the attempt to increase the battery""s capacity.
Next, the structural design employed in realizing another single-piece sealing plate by joining the cap-shaped terminal plate 14 and the filter 1 by welding makes the design of needed component parts complicated in the same way as the above and also results in a loss of the battery""s internal volume due to a complicated structure of the safety valve 2. Furthermore, when break down at the welding point is brought from an inadvertently weak welding in production process or corrosion, vibration and infliction during the use of the battery, the current path can not be secured and further a reduction of reliability in the sealing point is brought about by the breakage of the welded segment since only the side of the filter 1 of the sealing plate D1 is performing a sealing function between the sealing plate D1 and the metallic case 5.
In addition, with a cylindrical type alkaline storage battery, phenomena like excessive current flow are recognized which cause abrupt rise in the internal pressure and leakage of large amount of gas likely when an inappropriate charge circuit is used or a charge circuit is out of order or an inappropriate charging condition is set up. In order to cope with this unusual rise in the internal pressure under abnormal conditions and secure a safe operation of the battery, a safety valve mechanism as shown in FIG. 5 is usually employed. However, when the aforementioned unusually excessive current flows over a prolonged period, not only a safety control problem caused by a released gas and but also battery performance problems which are caused by drying up of electrolyte and accelerated deterioration of separators due to over heating. In such a case, normal performance is not recovered even if the charge current is returned to the normal level, may be resulted. Therefore, it is required of a sealing plate to include a reversible mechanism whereby the electric circuit is interrupted when an unusually excessive current such as above continues therein and the electric-circuit is preferably recovered when the internal pressure returns to the normal level.
The present invention aims at improving the safety control of the internal pressure and enhances the reliability of the electric current path while achieving a simplification of the mechanism as described above, and, at the same time, maintains the required internal volume of the battery and, further, also aims at realizing a new mechanism whereby interruption of excessive current flows and recovery of the electric current path upon reduction of the internal pressure are made possible.
What is disclosed by the present invention in dealing with the foregoing problems is as follows:
With a cylindrical type alkaline storage battery comprising a group of spirally wound electrode plates formed of belt-shaped positive electrode plates and negative electrode plates and separators, a metallic case containing the group of electrode plates therein and a sealing plate, the sealing plate comprises:
a cap-shaped terminal plate formed of a cap part and a flange; and
a disc-shaped filter provided with a gas venting hole near the center thereof and adjoining the underside of the flange of the cap-shaped terminal plate, wherein the edge of the metallic case is bent forcefully inward, thereby sealing a space between the metallic case and both of rims of the flange of the cap-shaped terminal plate and the disc-shaped filter together via a gasket.
As described in the above, by employing parts with simple construction such as before said cap-shaped terminal plate and a filter and a gasket and by employing simple means such as bending forcefully the edge of the metallic case inward, all operations of fixing the sealing plate, forming the structure of a sealing plate and sealing the space between the sealing plate and metallic case via the gasket are completed at one time. Therefore, a filter is no longer required to be bent at the edge thereof and one layer of the double layer at the edge thereof is no longer required, both of which are needed in the prior art battery structure, thus resulting in saving the space required to accommodate the components of complicated construction otherwise and enabling the loss in the available internal volume of the battery case to be minimized.
According to the present invention, the both of rims of the filter and the flange of the cap-shaped terminal plate are forced into the inside of the gasket by the edge of the metallic case that is bent forcefully inward. At that time, strong pressing force is applied to the foregoing two adjoining materials due to the elasticity of the gasket, thereby establishing a current path between the filter and the cap-shaped terminal plate, which are brought into a close contact with each other. Therefore, unlike the prior art battery, regardless whether welding is applied or not to join the filter and the cap-shaped terminal plate together or the condition at the junction thereof, high reliability of the current path can be ensured. In addition, the filter and the flange of the cap-shaped terminal plate are brought into intimate contact with the gasket, respectively, and high sealing reliability can be ensured without any influence imposed by the conditions of fractures at a welded spot.
Moreover, by making the cap-shaped terminal and filter detachable each other in establishing the adjoining structure and also making the gasket elastic, it is made possible for the contacting condition between the two surfaces of the flange of the cap-shaped terminal plate and the filter to be variable. On the other hand, there is a gas venting hole located near the center of the filter and the cap-shaped terminal plate can be made first to be imposed with the internal pressure before the filter by imposing a restriction on or suppressing a release of the pressure. When the aforementioned contact condition varies, the contact resistance between the flange of the cap-shaped terminal plate and the filter is varied accordingly, thereby bringing about a favorable reaction such as suppressing or interrupting electric current flow according to the internal pressure and recovering the electric current path when the pressure is reduced.
With a cylindrical type alkaline storage battery comprising a group of electrode plates formed of belt-shaped positive and negative electrode plates and separators and spirally wound and, a metallic case containing a group of electrode plates therein and a sealing plate provided with a safety valve inside thereof and sealing hermetically the top part of the metallic case, the sealing plate in a first exemplary embodiment of the present invention comprises:
a cap-shaped terminal plate formed of a cap part and a flange; and a disc-shaped filter provided with a gas venting hole near the center thereof and adjoining the underside of the flange of the cap-shaped terminal plate, wherein a gas exhaust hole is provided on the surface of the cap parts of the cap-shaped terminal plate, where no contacting with the filter takes place, also a safety valve is provided between the cap-shaped terminal plate and the disc-shaped filter, and the edge of the metallic case is bent forcefully inward, thereby a space between the metallic case and both of the rims of the flange of the cap-shaped terminal plate and disc-shaped filter, which are adjoining each other, is sealed together via a gasket.
With a cylindrical type alkaline storage battery comprising a spiral-shape group of electrode plates formed of belt-shaped positive and negative electrode plates and separators, a metallic case containing the group of electrode plates therein and a sealing plate to seal hermetically the top part of the metallic case, the sealing plate in a second exemplary embodiment of the present invention comprises:
a cap-shaped terminal plate formed of a cap part and a flange; and
a disc-shaped filter adjoining the underside of the flange and provided with a gas venting hole near the center thereof wherein the edge of the metallic case is bent forcefilly inward, thereby a space between the metallic case and both of the rims of the flange of the cap-shaped terminal plate and the disc-shaped filter, which are adjoining each other, is sealed together via the gasket.
With a cylindrical type alkaline storage battery comprising a spirally-shaped group of electrode plates formed of belt-shaped positive and negative electrode plates and separators, a metallic case containing the group of electrode plates therein and a sealing plate at the top part of the metallic case. The sealing plate in a third exemplary embodiment of the present invention comprises:
a cap-shaped terminal plate formed of a cap part and a flange; and a discshaped filter adjoining the underside of the flange of the cap-shaped terminal plate and provided with a gas venting hole near the center thereof, wherein at least one gas exhaust hole is provided on the flange of the cap-shaped terminal which is in contact with filter and the edge of the metallic case is bent forcefully inward, thereby a space between the case and both of rims of the flange of the cap-shaped terminal plate and the disc-shaped filter, which are adjoining each other, is sealed together via a gasket.
A fourth exemplary embodiment of the present invention is characterized by making the outer diameter of the flange of the cap-shaped terminal plate the same as the outer diameter of the filter in the first exemplary embodiment to the third exemplary embodiment, thereby enhancing the reliability of each respective finction realized by the present invention.
A fifth exemplary embodiment of the present invention is characterized by applying a sealing agent to the portion between the flange of the cap-shaped terminal plate and the filter in the first exemplary embodiment to the fourth exemplary embodiment. The performance enhances thereby the reliability in resistance to electrolyte leakage of the battery incorporating the present invention.
A sixth exemplary embodiment of the present invention is characterized by using a material selected from the group of fluorine resin, blown asphalt and silicon resin as a sealing agent in the fifth exemplary embodiment, thereby enhancing the reliability of sealing of the battery incorporating the present invention.
A seventh exemplary embodiment of the present invention is characterized by welding a part of interface between the flange of the cap-shaped terminal plate and the filter according to a laser welding method or a resistance welding method in the first exemplary embodiment to the fourth exemplary embodiment, thereby enhancing the reliability of the electric current path of the battery incorporating the present invention and also contributing to a production process simplification through integrated handling of components.